Message Processing Control in a Publish/Subscribe System

1. For use in a publish/subscriber system in which a published message originating with a publisher is identified by an associated topic string and originally includes a PubLevel value assigned by the publisher, a broker apparatus comprising: a receiver component for receiving the published message; a subscriber selection component for selecting a subscriber from a set of one or more subscriber candidates that have registered a subscription with the broker to receive published messages identified by the associated topic string, each of said subscriber candidates having an associated SubLevel value; a publication control component for changing the PubLevel value associated with the published message as a function of the SubLevel value associated with the subscriber selected by the subscriber selection component; and a transmit component for forwarding the published message to the subscriber selected by the subscriber selection component.

2. A broker apparatus according to claim 1 wherein the subscriber selection component eliminates from consideration any subscriber candidate having an associated SubLevel value greater than the current PubLevel value of the published message.

3. A broker apparatus according to claim 2 wherein the publication control component changes the PubLevel value associated with the published message to a value less than the SubLevel value of the selected subscriber.

4. A broker apparatus according to claim 3 wherein the subscriber selection component selects a subscriber having an associated SubLevel value less than and closer to the published message PubLevel value than the associated SubLevel value of any of the other subscriber candidates.

5. For performance in a broker apparatus in a publish/subscribe system in which a published message originating with a publisher is identified by an associated topic string and originally includes an associated PubLevel value assigned by the publisher, a method of processing a published message comprising: receiving the published message; identifying both a topic string associated with the published message and the value of the PubLevel value currently assigned to the published message; selecting a subscriber to receive the published message from a set of one or more subscriber candidates that have registered subscriptions with the broker apparatus to receive published messages identified by the topic string associated with the published message, each of said subscriber candidates having an associated SubLevel value; changing the PubLevel value assigned to the published message as a function of the SubLevel value associated with the subscriber selected to receive the published message; and sending the published message to the subscriber selected to receive the published message.

6. A method according to claim 5 wherein selecting a subscriber to receive the published message from a set of one or more subscriber candidates that have registered subscriptions with the broker apparatus to receive published messages identified by the topic string further comprises eliminating from consideration any subscriber candidate having an associated SubLevel value greater than the current PubLevel value of the published message.

7. A method according to claim 6 further comprising changing the PubLevel value assigned to the published message to a value less than the SubLevel value of the subscriber selected to receive the published message before the message is sent to said subscriber.

8. A method according to claim 7 wherein selecting a subscriber to receive the message from a set of one or more subscriber candidates that have registered subscriptions with the broker to receive published messages identified by the topic string further comprises selecting a subscriber having an associated SubLevel value less than and closer to the published message PubLevel value than the SubLevel value of any of the other subscriber candidates.

9. A computer program product for controlling the processing of messages at a broker apparatus in a publish/subscribe system in which a published message originating with a publisher is identified by an associated topic string and originally includes an PubLevel value originally assigned by the publisher, said computer program product comprising a non-transitory computer usable medium having computer usable program code embodied therein, said computer usable program code comprising: computer usable program code configured to receive the published message; computer usable program code configured to identify both a topic string associated with the published message and the value of the PubLevel value currently assigned to the published message; computer usable program code configured to select a subscriber to receive the published message from a set of one or more subscriber candidates that have registered subscriptions with the broker apparatus to receive published messages identified by the topic string associated with the published message, each of said subscriber candidates having an associated SubLevel value; computer usable program code configured to change the PubLevel value assigned to the published message as a function of the SubLevel value associated with the subscriber selected to receive the published message; and computer usable program code configured to send the published message to the subscriber selected to receive the published message.

10. A computer program product according to claim 9 wherein the computer usable program code configured to select a subscriber to receive the published message from a set of one or more subscriber candidates that have registered subscriptions with the broker to receive published messages identified by the topic string further comprises computer usable program code configured to eliminate from consideration any subscriber candidate having an associated SubLevel value greater than the current PubLevel value of the published message.

11. A computer program product according to claim 10 further comprising computer usable program code configured to change the PubLevel value associated with the published message to a value less than the SubLevel value of the subscriber selected to receive the published message before the message is sent to said subscriber.

12. A computer program product according to claim 11 wherein said computer usable program code configured to select a subscriber to receive the published message from a set of one or more subscriber candidates that have registered subscriptions with the broker apparatus to receive published messages identified by the topic string associated with the published message, each of said subscriber candidates having an associated SubLevel value, further comprises computer usable program code selected to select subscriber having an associated SubLevel value less than and close to the published message PubLevel value than the SubLevel value of any of the other subscriber candidates.